1. Technical Field
The present invention relates to a projector.
2. Related Art
Projectors have been used in the fields of presentation, home theater systems and the like. Such projectors include a projector that is provided with a light source device, a color-separating optical system for separating a light beam irradiated by the light source into a plurality of color light components, three optical modulators such as liquid crystal panels each for modulating a separated color light component in accordance with image information, a color-combining optical system such as a prism for combining the color light components modulated by the optical modulators, and a projection optical device such as a projection lens for projecting a combined optical image in an enlarged manner.
When this type of projector is used for business use as a data projector, a high-pressure discharge lamp with high relative spectral intensity in the wavelength band for green (approx. of 500 to 570 nm) or in the wavelength band for blue (approx. of 420 to 460 nm) is used as the light source in order to provide sufficient luminance to a projection image.
However, when the projector with the above-described light source is diverted to home use, the wavelength band for green is intense, so that a portion to be white of the projection image becomes greenish, causing reduction in brightness and contrast when trying to correct this problem by using the optical modulators.
To solve this disadvantage, there has been known an arrangement in which an optical filter for eliminating a predetermined spectral component is disposed on the downstream of a projection lens in the optical path (see, for example, JP-A-2004-45482).
The optical filter disclosed in the document is a reflective optical filter that includes a base and optical conversion films deposited on a light-incident surface of the base, the optical conversion films having different refractive indexes. Since the optical filter is disposed on the downstream of the projection lens in the optical path, an optical image irradiated from the projection lens passes through the optical filter, so that reduction in contrast of the projection image can be prevented.
However, reflection property of the optical filter disclosed in the above-described document varies depending on an incident-angle of the light beam. In addition, the projection lens is adapted to irradiate the light beam such that the light beam is expanded at a predetermined angle relative to the center of the optical path in order to form the projection image in an enlarged manner. Hence, the light beam forming a peripheral portion of the projection image has a large incident-angle relative to a light-incident side surface of the optical filter, causing variation in color between the peripheral portion and the middle portion of the projection image.